Suggestions:
Check that you have followed the instructions at the top of the file for how to set up mod_python.
Also I recommend checking that you have the file permissions set ok so that the user running the apache process can read them.
Start with a basic .jpeg in the root folder then work up from there.
Sorry man, I realise I am plaguing you at this point… this reply is the first time I’ve seen any reference to mod_python? Are there instructions I’m not seeing beyond the following?
# Setup instructions
# (install apache2), then...
# sudo a2enmod cgid
# sudo systemctl restart apache2
# sudo apt-get install python-svgwrite
I have done all the above from root and I am a little further on now I guess. I am now able to see files on the server, I’ve created a test_script which I am able to view at
http://localhost/cgi-bin/dhw_tank/test_script , but
http://localhost/cgi-bin/dhw_tank/dhw_tank.cgi?temps=54.6,52.6,51.3,50.6,39.1,25.0&fmt=svg is still flagging an internal server error. Does this help point to anything obvious I am doing wrong?
Also noticing, I went down the instructions for the 8th time, and when i get to install python-svgwrite I get the following
root@pi:~# sudo apt-get install python-svgwrite
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
E: Unable to locate package python-svgwrite
Is this the problem?
right, bit more digging - i can finally see the image in my web browser. I had to run the following instead so maybe the instructions need updated?
sudo apt install python3-svgwrite
So, my final struggle. The markdown card… I believe I have it set up correctly, the local host has been redirected accordingly, the sensor names have been adjusted accordingly and the 2 additional have been removed - but no joy seeing a picture.
Just 
Same thing happens even if i modify the image path to the test URL provided in the instructions (which is viewable in web browser). Any final words of advice?
I have a home assistant shortcut in chrome that opens it in a separate window - seems it’s what was blocking it appearing… So all is now working as intended! Thanks for all the help and patience bud, much appreciated!
I want this also on my home assistant. What did you do to get the script to run? I’m a beginner really with the Home assistant. Got a lot integrated so far with Tuya local / A/C units / Media players etc. But I couldn’t make heads or tails on how to run the python script Dave made.
Able to help with this?
as much as i got it working, im currently running down other avenues of making it suit my setup a little better.
I have it running on an apache server on another Pi - however because i am unlucky enough to not have a static IP at home, it’s only viewable in the house. I can’t check it out “visually” from work.
Maybe a little more info on what kind of setup you have and I may be able to help out a bit more?